Diisopropyl 2-[(4-nitrobenzoyl)amino]propanedioate

The title compound crystallizes in the space group C2 with two molecules in the asymmetric unit.


Structure description
The title compound [alternative name: diisopropyl 2-(4-nitrobenzamido)malonate] was made in an attempt to make a compound with an N 3 cyclic ring. The starting material for this compound has been used previously to make symmetrical and unsymmetrical secondary amines (Kattamuri et al., 2017). The title compound crystallizes in the monoclinic space group C2 with two molecules in the asymmetric unit (Z = 8). Molecule A contains nitro group N1-O1-O2, and molecule B contains nitro group N3-O8-O9 (Fig. 1). Both nitro groups are almost coplanar with their attached phenyl rings [dihedral angles = 3.7 (11) for molecule A and 3.3 (8) for molecule B]. An overlay of the two molecules indicates an almost complete overlap with only slight deviations in the ester groups (r.m.s. deviation = 0.268 Å ; Fig. 2). The dihedral angle between the phenyl rings is 38.0 (3) . The closest interactions in the packing are observed between the two molecules in the asymmetric unit ( Fig. 3): an N3-O8Á Á Á interaction [O8Á Á ÁCg1 = 3.272 (6) Å , Cg1 is the centroid of the C1-C6 ring] and a C9 O4Á Á Á interaction [O4Á Á ÁCg2 = 3.552 (7) Å , Cg2 is the centroid of the C17-C22 ring].

Synthesis and crystallization
In an oven-dried Schlenk reaction vessel, diisopropyl 2-[(tosyloxy)imino]malonate (185.7 mg, 0.5 mmol, 1.0 equiv.) was dissolved in anhydrous THF (5 ml) under Ar and cooled to 273 K on an ice bath. To the cooled solution, Et 3 N (1.0 mmol, 2.0 equiv.) and data reports hydrazine (0.5 mmol, 1.0 equiv.) were added. The reaction mixture was allowed to stir at 273 K for 2 h. After full conversion as indicated by TLC, Et 3 N (1.0 mmol, 2.0 equiv.) and 4-nitrobenzoyl chloride (92.8 mg, 0.5 mmol, 1.0 equiv.) were added to the reaction mixture. After stirring the reaction mixture for 3 h at 273 K, a saturated NaHCO 3 solution was added and the mixture was extracted with diethyl ether. The combined organic fractions were concentrated in vacuo. The crude product was purified using silica gel flash column chromatography to afford the title compound (90.0 mg, 51% yield). Crystals were obtained by dissolving the compound in a minimum amount of CH 2 Cl 2 and layering with hexane at 295 K.

Refinement
Crystal data, data collection and structure refinement are summarized in Table 1.

Figure 3
Packing diagram for the title compound.

Figure 1
Molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. Hydrogen atoms are omitted for clarity.

Figure 2
Overlay plot of the two molecules in the asymmetric unit. Molecule A is shown in green, molecule B in red.

data-1
IUCrData (  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.